For example, the document U.S. Pat. No. 8,116,923 B2 discloses a monitoring device and a monitoring method of the aforementioned type. Such a monitoring device extracts from a database a predetermined approach flight path angle towards the landing runway when the aircraft is in the approach phase, and determines whether a first difference between the position of the aircraft and the predetermined flight path angle is greater than a first predetermined threshold value.
The monitoring device then determines, when the first difference is greater than the first predetermined threshold value, whether a second difference between the angle of trajectory of the flight path of the aircraft and a predetermined angle of the approach flight path angle is greater than a second predetermined threshold value. The monitoring device then generates a system alert, directed to the crew of the aircraft and in particular to the pilot, warning of the approach phase instability when the second difference is greater than the second predetermined threshold value.
However, such a monitoring device only addresses a specific aspect of situations wherein the approach is not stabilised and thus generates a relatively large number of false alerts, also referred to as false alarms, which generally has a disturbing and disruptive effect on the crew of the aircraft. This is then quite likely to diminish the safety of the flight.